Influences Of Different Storage Temperatures On Colour Of ‘Jinxiu’ Peach Fruits

Peach is one of the most important fruit in theword. Yellowed-fleshed peach is widely appreciated for its bright color, characteristic aroma and richness in nutrition. Color is an important factor that affects the peach quality and commodity value. However, the regulation of postharvest fruit color is less known up to date. The mature stage of peach concentrats in the summer. Temperature plays an important role in the process of postharvest ripening. In this study, ‘Jinxiu’ peach fruits are storaged at different temperatures: low temperature(5 ℃) and different shelf life temperature(15 ℃、25 ℃、room temperature and 35 ℃). The content of carotenoids and the expression level of genes in relation to metabolic pathways of carotenoids are measured to investigate the regulation of the color change during storage at different temperatures and the mechanism of carotenoids metabolism responsing to different shelf life temperatures. This study provide some theoretical foundation for postharvest peach fresh-keeping. The main results are as follows:1. Changes of carotenoids content analyzed by High Performance Liquid Chromatography(HPLC) shows that the major carotenoid compositions of postharvest ‘Jinxiu’ peach fruits are violaxanthin, 9-cis-violaxanthin, luteoxanthin, β-carotene, lutein and β-crytoxanthin. The content of carotenoid in fruit peel are significantly higher than in flesh. Total carotenoid content of peel and flesh of peach fruit samples stored at 5 ℃ increases during the early stage of storage period, and decreases in the later stage of storage period. The accumulation peak of carotenoids in peel and flesh respectively appeares on 15 d and 10 d of storage period. Total carotenoid content of peel and flesh of peach fruit samples stored at different shelf-life temperatures increases during whole storage period.2. 4 stable genes were selected from RNA-seq analysis and 12 traditional reference genes were selected as candidate reference genes. qRT-PCR and two softwares(geNorm&NormFinder) are used to evaluate the stability of these genes in five different peach experimental sets, including peel and flesh of peach fruit samples stored at different temperatures(5 ℃,15 ℃, 25 ℃, room temperature and 35 ℃), fruit samples of different developmental stage, different peach plant tissues(root, stem, leaf, flower and fruit), and overall performance in all sample sets. The results from the two software analyses show that PpeIF-1A and PpMUB6 are the most appropriate reference genes in all the five sample setups, while PpRPS28, PpRPT-5A and PpAKT3 are unsuitable control genes with variable expression patterns.3. The expression level of genes related to carotenoid metabolic pathways are measured with PpeIF-1A and PpMUB6 as internal genes. The results show that carotenoid metabolism of postharvest peach fruits are still regulated by transcriptional level. It differs in expression trends of genes related to carotenoid metabolic pathways in ‘Jinxiu’ peach fruits when storaged at variant tempreatures. The expression trends of PDS, ZDS and LCYB1 are in line with the total carotenoid content of the fruits(peel and flesh) storaged at 5 ℃, as is the same with CRISTO at 25 ℃. The expression trends of CRISTO、LCYB2a、LCYE and HYE are in accordance with the total carotenoid content of the peel storaged at 35 ℃。 Additionally, the total carotenoid content of the flesh storage at 35 ℃ has common with the expression trends of CRISTO and LCYE.